1. Field
The present disclosure relates to tappets and nozzles of phosphor dispensers for coating a phosphor liquid on a light-emitting device package.
2. Description of the Related Art
Light-emitting device chips, for example, light-emitting diodes (LEDs), are semiconductor devices that realize various light colors by configuring a light source having a PN junction of compound semiconductors. LEDs have a long lifetime, may be miniaturized and manufactured light, and may be driven at a low voltage due to a high directionality. Also, LEDs are strong against impact and vibration, do not require a preheating time and a complicated driving, and may be packaged in various types. Accordingly, LEDs may be applied for various purposes.
In order to realize a light-emitting device that emits white light, generally, a phosphor layer in which a yellow phosphor or a mixture of a green phosphor and a red phosphor is formed on a blue light-emitting diode. The phosphor layer is formed on a light-emitting device chip by coating a phosphor liquid, in which a phosphor is mixed with an epoxy resin or a silicon resin, using a phosphor dispenser. Through a drying process of the phosphor layer, a light-emitting device package is manufactured.
A phosphor dispenser includes a nozzle through which a phosphor liquid is ejected and a tappet that pushes the phosphor liquid towards the nozzle while the tappet is moving towards the nozzle.
A conventional tappet and nozzle are formed of materials having a high abrasion resistance, for example, tungsten carbide, or wear-resistant ceramics, for example, silicon nitride, silicon carbide, or zirconia.
However, the tappet and nozzle are worn out by the phosphor due to repeated and high-speed reciprocal movement of the tappet, and accordingly, it is difficult to eject a uniform quantity of a phosphor liquid and the life expectancy of the tappet and nozzle is shortened.